Location of fire detection units in forests is influenced by a set of conflicting parameters representing effectiveness (degree of screening, degree of overlapping), cost of installation and maintenance, reliability and security. This research work proposes a multicriteria methodological frame based on disaggregation-aggregation UTA II method and MIIDAS system in order to support the selection of positions and the arrangement of the fire detection units in the forest. The methodological frame was utilised for a real world application concerning the design of Lycabettus Hill fire detection system.